This invention relates to a system for, and method of, providing a seamless inflatable member such as an inflatable bag or seat belt, in a vehicle and inflating the member to protect an occupant when a collision involving the vehicle occurs.
Safety of occupants in vehicles is an important concern to manufacturers of the vehicles and to the occupants of the vehicles. The manufacturers have disposed seat belts, some partially or wholly inflatable, and inflatable air bags in the vehicles to protect the occupants when collisions involving the vehicle occur. An inflatable member (this term is used herein to describe an air bag as well as an inflatable belt or an inflatable belt portion) becomes inflated upon the occurrence of a collision involving a vehicle to reduce the occupant""s velocity and deceleration below unacceptable rates and to limit the occupant""s movement to enhance the occupant""s safety. Many manufacturers have started to provide inflatable members for occupants of the front driver seat of an automobile. Most automobile manufacturers now provide 3-point seat belts which include a shoulder belt portion and a lap belt portion. Most aircraft passenger seats are now provided with 2-point seat belts which include only a lap belt portion. The number of points refers to the number of anchors or retainers that affix the safety belt system for an occupant.
Perhaps the most significant consideration in a vehicle containing an inflatable member relates to the fact that such a member cannot begin to restrain the occupant""s motion during the vehicle collision until the occupant has moved into engagement with such member. Air bags that are typically deployed from the dashboard or steering wheel waste an important portion of the time and deceleration space available to protect the occupant against injury. This markedly reduces the occupant""s protection from the level that can be provided if the restraint is initiated before the occupant has moved within the vehicle after initiation of the vehicle collision.
Non-inflatable seat belts now in use suffer from certain significant disadvantages. For example, although certain selected designs of seat belts can, through the use of pre-tensioning devices, begin a restraint of the occupant earlier than the restraint provided by an air bag deployed from the dashboard or steering wheel, such belts do not provide for control of the occupant""s head motion. This shortened deceleration time, however, has caused markedly higher decelerations and loadings, at least of the occupant""s head, and has produced less than desirable results from the standpoint of injury thereto.
Seat belts are also often of narrow physical construction and thus have not provided for the distribution of the restraining loads over wide areas of the occupant""s body. This has resulted in unnecessarily high loads being imposed upon the occupant over the limited portion of the occupant""s body in engagement with the seat belt when a collision involving the vehicle occurs. Additionally such belts have possessed an elongation that, in many situations, has allowed the head of an occupant to strike the steering wheel or the dashboard when the occupant has been seated in a front seat.
Furthermore, the spooling out of the webbing material in the seat belt and the stretching of the seat belt have contributed to an increased duration of the unrestrained motion of the occupant before any effective restraint. This has meant that the motion of the occupant has had to be brought to a stop in a shorter time than would have been possible if the seat belt had not elongated. This has contributed to the production of undesirably high rates of motion and deceleration on the occupant during the restraint imposed by the seat belt on the movement of the occupant.
Use of inflatable seat belts of the types known in the prior art does not overcome all of the deficiencies and disadvantages discussed above. Many prior attempts at eliminating these deficiencies and disadvantages with inflatable belts have included seat belts with a pair of inflatable sections within the belt (one for the shoulder belt portion, the other for the lap belt portion) and have additionally required the inflation of these sections to be accomplished by larger than desirable inflators. Many previous attempts at producing satisfactory inflatable belts have also resulted in serious problems with storing the pair of inflatable sections in the vehicle and have required these inflatable sections to occupy areas that interfere with entrance and egress of the occupant respectively into and from the vehicle.
The deficiencies and disadvantages of many prior art inflatable seat belts have also required the inflators to be positioned at the releasable coupling member and the retainer to be positioned at the sides of the seats. This duality of inflatable sections has caused many significant problems. One of these has been that the inflatable gases have had to pass through conduits located at the buckle attachment point of the belts that are in themselves releasable. This makes the belts and the inflator difficult to package and to operate.
The inflatable belts with dual inflatable sections have had to be attached to mechanisms which allow for variable lengths of the belts to be deployed due to variable sizes and positions of the occupants within the vehicle. This has required the inflator to be located at the buckle location with the aforementioned deficiencies or has required the heavy mass of the inflator to be contained within the inflatable sections of the seat belts. Furthermore, the duality of inflatable sections has required additional inflators, squibs, wiring and the like to be used since both of the inflatable sections in the pair have had to be simultaneously inflated.
Most inflatable seat belts known in the prior art have other significant deficiencies and disadvantages. For example, they do not adequately protect the occupant""s neck and head in a side collision. Furthermore, they also do not adequately protect the occupant""s lower extremities. This results from the fact that the front seat occupant""s lower extremities tend to slide forward against the instrument panel at the time of the collision while the occupant in the rear seat tends to slide against the rear of the front seat. This xe2x80x9csubmariningxe2x80x9d has caused the occupants to incur injuries to the lower extremities.
The inflators associated with most prior inflatable seat belts have operated in an inefficient thermodynamic manner, and thus have required relatively large amounts of pyrotechnic materials to be provided in the inflators so that the size and weight of the inflators have had to be increased to undesirable proportions. The amount of the pyrotechnic material required in most of the inflators of the prior art has been roughly between fifty percent (50%) to one hundred percent (100%) more than is used in the preferred inflator of this invention. As a result, acceptable packaging of most prior art inflatable belts and the inflator within a vehicle has been precluded.
The configuration and composition of the combustible materials used in most existing inflators have also produced relatively slow inflation systems. These slow inflation systems, while useful for air bags, have not been useful for inflatable seat belts since such restraints must deploy in less than one fourth of the time for the deployment of a typical air bag, to be effective, particularly to provide occupant protection from side impacts. The deceleration distance of a vehicle involved in a side collision and the time interval between the initiation of the side impact against the vehicle and the striking of the occupant against an interior vehicle surface are greatly reduced relative to the distance and time for a front impact.
The combustible materials for some of these known systems have also required filters to collect the solid particulates that are produced in operation. Other known systems have utilized pyrotechnic grains of such size that grain fracture and cracking have occurred and have caused variations in the combustion surface, thereby detrimentally affecting the burning rates within the grains and hence the inflation time. Furthermore, when large grains have been utilized with slow burning rates, the variations in performance over the range of operating temperatures have been undesirably large, resulting in variations in protection. For example, assuming a 40-50 millisecond function time, the changes in the burning rate of the pyrotechnic material have caused the function time of the inflator to vary by approximately xc2x120% when the temperature has been varied between 175xc2x0 F. and xe2x88x9265xc2x0 F. This considerable percentage change in the burning rate has produced a change in overall function time of approximately 15-20 milliseconds, an appreciable portion of the time available to an air bag to decelerate the movement of the occupant, given that a typical frontal impact of an automobile lasts only about 120 milliseconds.
This invention provides a system which overcomes the above disadvantages and deficiencies. It comprises a seat belt combining a seamless hollow inflatable belt portion disposed across and adjacent the occupant""s body which becomes tightened against the occupant""s body when the inflatable portion becomes inflated. xe2x80x9cHollowxe2x80x9d as used herein in reference to a textile structure means that such structure is capable of being inflated. In a first preferred embodiment, it comprises a 3-point seat belt combining a seamless generally tubular inflatable shoulder belt portion disposed across and adjacent the occupant""s chest, neck and head and an interconnected lap belt portion which becomes tightened against the occupant""s lap when the inflatable portion becomes inflated. In a second preferred embodiment, it comprises a 2-point seat belt having a seamless generally tubular inflatable belt portion disposed across and adjacent the occupant""s lap which becomes tightened against the occupant""s lap and extends upward toward the occupant""s chest when the inflatable portion becomes inflated. Either of these enhanced restraints prevent the occupant in a front seat from sliding against the instrument panel or the steering wheel at the time of vehicular impact, thereby protecting against injury to the occupant""s knees and lower extremities. Either of these enhanced restraints also prevents the occupant in a rear seat from sliding against the back of a front seat.
Furthermore, in the first embodiment that includes an inflatable shoulder belt portion, when inflated, the inflatable generally tubular belt portion shortens in effective length and displaces away from the chest of the occupant to provide, in combination, pretensioning of the inflatable belt portion, load distribution and a support cushion for the head in frontal collision. Additionally, by passing the inflatable belt portion across the shoulder and alongside the head, the inflatable generally tubular belt portion protects the occupant""s neck and head from injury due to side impact.
An suitable inflator which responds almost instantaneously when a collision involving the vehicle occurs is described in WO 97123367 published Jul. 3, 1997, entitled xe2x80x9cInflatable Seat Belt Systemxe2x80x9d, naming Donald J. Lewis as inventor, which is incorporated herein by reference. For example, the inflator provides for the inflation of the inflatable belt portion in approximately ten milliseconds (10 ms) after being triggered by the vehicle collision. This is enabled in part by the use of a small pressure volume of approximately two (2) cubic inches in the inflator. This inflator is adapted for use with small particles of a pyrotechnic material, which provide a large surface that enhances the burning rates of such particles to provide for gas generation rates up to approximately ten (10) times greater than that of the inflators of the prior art. Furthermore, the relatively small amount of the pyrotechnic material in this inflator produces a minimal amount of any noxious by-products or noxious smells. This inflator is further advantageous in that all of the components in the inflator are disposed within a housing and in that a gas in the housing flows through a short outlet directly into the inflatable belt portion to inflate the inflatable belt portion almost instantaneously after triggering by the vehicle collision.
The gas flowing through the outlet of the inflator inflates an inflatable belt portion disposed across the occupant""s body and attached to a vehicle support structure (e.g. a pillar behind the occupant""s seat, the floor or a structural seat affixed to the vehicle support structure), thereby protecting the occupant""s body.
The inflatable belt portion of this Invention may be integrally formed as by weaving to a webbing defining the remainder of the belt portion, or attached as by multiple stitching to webbing defining the remainder of the belt portion. Some of this stitching may be configured to become progressively, but not completely, detached to dissipate the forces imposed on the inflatable belt portion when the inflatable belt portion becomes inflated. Where the inflatable belt portion is disposed diagonally across the chest of the occupant and is joined to a lap belt portion, the lap belt portion is preferably arranged to slideably extend through an opening in a coupling member adjacent the inflatable belt portion and laterally across the occupant""s lap.
In such an arrangement the lap belt portion becomes tightened against the occupant""s lap when the inflatable belt portion becomes inflated. The lap belt portion is removably attached as by the coupling member to a retainer at the inner side of the seat. When the coupling member is detached from the retainer, the lap belt portion becomes disposed (e.g. wound) on a retractor to dispose the inflatable belt portion near the outboard seat side between the support structure (e.g. the pillar behind the driver""s seat) and the retractor. The occupant can then enter and exit the vehicle without encumbrance. Alternatively, the retractor for the lap belt portion may be connected to the seat itself, and the seat attached to a vehicle support structure, e.g. the floor or frame of the vehicle.
The inflatable belt portion is preferably enveloped within a cover made from any suitable material; for example, a polyester or a nylon. The cover may be made from a single piece of material attached at its opposite ends as by stitching to define a flattened cylinder enveloping the inflatable belt portion. The cover stitching progressively separates as the inflatable belt portion becomes progressively inflated in a direction away from the inflator. The cover is advantageous in that it may designed to assist in providing for a controlled inflation of the inflatable belt portion in a direction away from the inflator. It also minimizes degradation of the material forming the inflatable belt portion as from ultraviolet light and protects the inflatable belt portion from degradation as from chafing against the occupant. A stiffener may be disposed in the cover against the inflatable belt portion to prevent the inflatable belt portion from twisting. Alternatively, the cover may be made from a frangible fabric material designed to burst open as the inflatable belt portion is inflated. Alternatively, the inflatable belt portion may contain an integral stiffener to prevent the inflatable belt portion from twisting. The cover may extend beyond the inflatable belt portion to define the remainder of the belt portion in place of standard webbing.
A switch may be disposed in the retainer in an open position. When the coupling member is disposed in the retainer, the switch becomes closed. The switch is included in an electrical circuit which is operative to initiate the combustion of the pyrotechnic material within the inflator, upon the occurrence of a collision involving the vehicle, when the switch is closed. In this way, the inflatable belt portion can become inflated upon the occurrence of a collision involving the vehicle only when the inflatable restraint system of this invention is connected to protect the occupant""s body. This importantly avoids unnecessary deployment and attendant replacement costs of repairing a vehicle after a collision.